Recently there has been increased interest in the use of hydrogen as an automotive fuel and in many processes there is a requirement for hydrogen gas. These processes vary widely but particularly include refining operations. In most such operations, sour gas streams are also produced. These sour gas streams may be the result of other refining operations, such as desulfurization, crude oil distillation and the like. Further, natural gas streams containing acid gas components may be available to the refining operation. As a result of the removal of the acid gas components from such gases and the recovery of the acid gas components from other refinery streams, a considerable amount of sulfur is typically recovered by the use of Claus plants.
Claus plants are considered to be well known to the art and basically comprise the partial oxidation of an acid gas stream to oxidize any hydrocarbons present in the stream and to convert the stream to a stream which contains hydrogen sulfide and sulfur dioxide in a 2:1 ratio. The sulfur dioxide and the hydrogen sulfide are then reacted over well known catalysts in the Claus process in successive stages to produce sulfur and an exhaust gas stream, which after processing in a tail gas clean up unit as well known to the art, comprises primarily carbon dioxide and water. Such processes produce sulfur but in many instances the amount of sulfur available from such processes exceeds the demand for sulfur. Further there is a need for hydrogen in refining and other operations and for fuel.
Carbon black has been produced by a thermal carbon black process which consists of two furnaces which are used in alternate heating and production periods of about five minutes with each of the furnaces containing a network of heat resistant bricks. These are heated with natural gas and air. At a temperature of about 1400° C., the air is switched off and only natural gas is introduced for pyrolysis. Since this reaction is endothermic the temperature falls. At about 900° C. a new heating period is necessary. The products leaving the furnace are typically carbon black particles and nearly pure hydrogen gas. Ullman's Encyclopedia of Industrial Chemistry 5th Ed., Vol. A5, 1989.
It is also well known that acetylene can be used to produce acetylene black, which has slightly different properties than carbon black, but also results in the production of hydrogen, although less hydrogen is produced with acetylene than with saturated light gases, such as methane.
A further disclosure of thermal black processes is shown in Kirk-Othmer Encyclopedia of Chemical Technology, 4th Ed., Vol. 4, 1992, pp. 1053-1054.
Such processes are considered to be well known to those skilled in the art and require the use of substantial heat input to thermally decompose methane or other light hydrocarbon gases into carbon particles and hydrogen gas. The use of such processes results in the production of a hydrogen gas stream which contains particulate carbon. This carbon is difficultly separated from such streams and accordingly an improved process has been sought whereby the carbon is readily removed from such streams.
In view of the need for hydrogen and the excess capacity available for sulfur production, improved methods for the production of hydrogen utilizing the excess sulfur have been sought.